The present application relates generally to a sensor system for detecting obstacles on a runway or defined other region. More particularly, the present application relates to a combined airborne radar or other airborne sensor system that is capable of detecting obstacles within a defined region or runway and is capable of using signals from multiple sources.
Incursion systems, such as runway incursion systems, are utilized to determine if an obstacle is in the path of an aircraft or other vehicle. Conventional runway incursion systems are generally one of two types. The first type utilizes signals cooperatively provided from the obstacle on the runway; the second type utilizes radar or other electromagnetic energy signals to actively sense the presence of an obstacle on the runway without the obstacles active cooperation.
Incursion systems, such as runway incursion systems, are utilized to determine if an obstacle is in the path of an aircraft or other vehicle. Conventional runway incursion systems are generally one of two types. The first type requires equipment operating on the obstacles or some form of ground-based infrastructure. The aircraft that is to be protected relies on operating equipment not on the aircraft. These systems are not stand-alone systems. The second type requires neither ground infrastructure nor the obstacle to be equipped in a special way. These are stand-alone systems. Stand-alone systems treat the obstacle as a target or the obstacle as a source or reflector of electromagnetic energy. Radar, light detection and ranging (LIDAR) systems, forward looking infrared (FLIR) systems, or optical camera based systems are examples of this stand-alone obstacle detection system type. Conventionally, the first type of runway incursion system relies upon principles associated with traffic alert and collision avoidance system (TCAS) and automatic dependent surveillance broadcasts (ADS-B) systems.
TCAS systems are required for all airliners flying in the United States air space today. TCAS devices have been designated to interrogate transponders of other aircrafts, sometimes referred to as intruder aircraft. The TCAS system evaluates the threat of collision with the other aircraft and coordinates an avoidance maneuver for the aircraft.
ADS-B systems are capable of providing position, velocity, and status information broadcast from an aircraft at regular intervals using information obtained from global positioning system (GPS) satellites and onboard systems. ADS-B systems may use the Mode S transponders and provide transmissions at regular intervals. Accordingly, ADS-B transponders need not be interrogated.
In an ADS-B system, a Mode S transponder may be disposed in a first aircraft that continuously emits a squitter message. The squitter message is a radio frequency (RF) signal that is generated by the radio-based transponder. In an ADS-B system there is not necessarily a reply to the ADS-B squitter message.
In one conventional runway obstacle detection system of the first-type, objects which may enter a runway, such as baggage carts, runway tugs, other aircraft, emergency vehicles, maintenance vehicles, etc., may carry transponders which provide location information. The location information can be generated from a GPS receiver (e.g., in an ADS-B type system). The transponders may relay information to a central control system which determines whether the object is on the runway. The location information can be provided directly to the aircraft or to the aircraft from the central control system.
Such a system requires that all objects which would potentially incur the runway space would be tagged with a transponder and all transponders remain functioning properly. In many situations, such as in underdeveloped areas, for example, in third world countries, or small airports and the like, sufficient infrastructure may not be available to support tagging each cart with a transponder and to have an appropriate central control system. Further, such systems cannot provide transponders to obstacles that cannot be tagged. For example, deer and other large animals may present a hazard if they wander onto a runway.
U.S. Pat. No. 6,850,185, entitled, “Runway Obstacle Detection System and Method” invented by Woodell and assigned to the Assignee of the present application describes an example of the second-type of conventional runway incursion system. U.S. Pat. No. 6,850,185 describes a weather radar system that utilizes active sensing of obstacles by transmitting electromagnetic beams and receiving the beam that bounces off obstacles in the path of the aircraft. This system does not require the obstacle to operate in a cooperative way. Therefore, this system can be considered both stand-alone and non-cooperative in nature. U.S. application Ser. No. 10/941,616 filed by Woodell et al. on Sep. 15, 2004 and assigned to the Assignee of the present application discloses a radar for detecting obstacles. U.S. Pat. No. 6,850,185 and U.S. patent application Ser. No. 10/941,616 are incorporated herein by reference. Such radar-based obstacle systems are subject to all the accuracy issues, detection rate issues and false alarm rate issues inherent in a radar-based detection system.
In another cooperative conventional runway obstacle detection system, land-based radar systems are used to detect runway obstacles. Land-based radar systems require infrastructure at each airport and can be susceptible to similar difficulties associated with airborne-based obstacle detection systems. An L-band system is being considered which uses signal transmission times as opposed to GPS systems to determine location. NASA is developing a runway incursion prevention system (RIPS) based upon ADS-B equipped aircraft, an airport database and an L-band data path.
Conventional incursion systems of the first and second-type have disadvantages. For example, ADS-B-type runway incursion systems cannot provide protection against vehicles or other obstacles that are not equipped with ADS-B transponders. If construction equipment does not include an ADS-B transponder, that equipment does not appear as an obstacle in an ADS-B system. Although weather radar systems and other sensors can detect obstacles that do not include transponders, weather radar systems and other sensors are not able to duplicate the positional accuracies, detection rates, and low false alarm rates associated with ADS-B-type systems. Further, weather radar systems and other sensors may not be able to detect obstacles that are shielded by other solid obstacles or obstacles that are susceptible to inaccurate detection by radar techniques.
Conventional runway alerting and annunciation systems may be used at the pilot interface. However, such systems may be disadvantageous as alerts by the system are called out aurally to the pilot. Such systems produce annunciations of location state changes of the aircraft. State changes such as entering or exiting an active runway or taxiway are annunciated even if these state changes do not represent an active threat. Such aural warnings may be distracting amongst the other chatter and alarms which pervade the cockpit. Accordingly, it is desirous to reduce the number of “false alarms” provided by runway incursion systems.
Accordingly, there is a need for a more accurate obstacle detection system which does not solely rely upon radar sensing or ADS-B based sensing. Accordingly, there is also a need for a radar system that allows the aircraft to operate autonomously in the U.S. and worldwide at any airport whether the airport being a minor airport or a major airport or whether the airport is in the U.S. or in any country. Further, there is a need for a runway obstacle detection system in which accuracy is increased and false alarms are decreased.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.